The present invention relates generally to automotive HVAC systems and methods of operating such HVAC systems.
Automotive HVAC systems are well known and are utilized for heating and cooling the passenger compartments of vehicles. Hybrid vehicles, which utilize a battery and an intermittently operated internal combustion engine for vehicle propulsion, have difficulty keeping the passenger compartment cool when the engine is off. When the engine is off, the HVAC compressor, typically run by a clutch connected to the engine, is also off and the temperature in the passenger compartment can rise quickly. The hybrid vehicle is most efficient when the engine is not running and, therefore, any extended increment of time that the engine is off increases fuel savings and reduces emissions.
It is desirable, therefore, to provide an HVAC system that allows for extended engine off time in hybrid vehicles while keeping the passenger compartment of the vehicle cool and also for precooling in conventional vehicles.